From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5D65CC0015E for ; Fri, 11 Aug 2023 10:15:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231954AbjHKKPf (ORCPT ); Fri, 11 Aug 2023 06:15:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60404 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233517AbjHKKPb (ORCPT ); Fri, 11 Aug 2023 06:15:31 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 53B8D2132 for ; Fri, 11 Aug 2023 03:15:05 -0700 (PDT) Received: from canpemm500009.china.huawei.com (unknown [172.30.72.53]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4RMfh85Z1XzCrqw; Fri, 11 Aug 2023 18:11:04 +0800 (CST) Received: from [10.67.102.169] (10.67.102.169) by canpemm500009.china.huawei.com (7.192.105.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Fri, 11 Aug 2023 18:14:34 +0800 CC: , Barry Song <21cnbao@gmail.com>, , , , , , Subject: Re: [PATCH] perf/smmuv3: Add platform id table for module auto loading To: Liang Li References: <20230807122233.28563-1-yangyicong@huawei.com> <23fe3d9a-cb4d-3479-0581-eefec193bc72@huawei.com> From: Yicong Yang Message-ID: Date: Fri, 11 Aug 2023 18:14:33 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.102.169] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To canpemm500009.china.huawei.com (7.192.105.203) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/8/9 20:11, Liang Li wrote: > Hi Yicong, > > Thanks for your reply, > > On 2023-08-09 14:31, Yicong Yang wrote: >> Hi Barry, Liang, >> >> On 2023/8/9 13:47, Barry Song wrote: >>> On Wed, Aug 9, 2023 at 1:01 PM Liang Li wrote: >>>> >>>> On 2023-08-07 20:22, Yicong Yang wrote: >>>>> From: Yicong Yang >>>>> >>>>> On ACPI based system the device is probed by the name directly. If the >>>>> driver is configured as module it can only be loaded manually. Add the >>>>> platform id table as well as the module alias then the driver will be >>>>> loaded automatically by the udev or others once the device added. >>>>> >>>> >>>> Please consider revise the long log to clearly express the purpose of the >>>> changes in this patch: >>>> >>>> - What's the exact issue the patch is addressing >>>> - Why the changes in this patch can fix the issue or make something working >>>> - Consider impact of the changes introduced by this patch >>>> >>>> These info may help reviewers and maintainers .. and yourself on code merge. >>> >>> years ago, i found a good doc regarding this, >>> https://wiki.archlinux.org/title/Modalias >>> >>> guess it is because /lib/modules/$(uname -r)/modules.alias fails to contain smmu >>> driver without the MODULE_DEVICE_TABLE, isn't it, yicong？ >> >> Yes I think it's the reason. I didn't find summary in kernel docs for the modalias >> as well as the uevent mechanism. Arch wiki has a well illustration for the modalias >> and suse[1] describes how this is used by the udev for module auto loading. >> >> For my case I'm using a ACPI based arm64 server and after booting the arm_smmuv3_pmu.ko >> is not auto loaded by the udevd since we aren't providing this information. In order >> to support this we need to provide this MODULE_DEVICE_TABLE() when the smmu pmu added >> as a platform device, then the userspace udev can know which module to load after the >> device is added. >> > > Then what's the purpose of the added '.id_table = ...' line in the previous > patch ? > > > Based on above clarification, the updated DEVICE_TABLE would update modalias > as expected, right ? ok, it's lack of illustration in the commit. If we're going to use MODULE_DEVICE_TABLE we need a platform id table. So I add it and I found it weired if we have a id table but not use it for probing, so I also initialize .id_table. I found there's also an another way to implement this by used MODULE_ALIAS(), and no need to add an id table. Maybe this way is less controversial. diff --git a/drivers/perf/arm_smmuv3_pmu.c b/drivers/perf/arm_smmuv3_pmu.c index 25a269d431e4..4c32b6dbfe76 100644 --- a/drivers/perf/arm_smmuv3_pmu.c +++ b/drivers/perf/arm_smmuv3_pmu.c @@ -984,6 +984,7 @@ static void __exit arm_smmu_pmu_exit(void) module_exit(arm_smmu_pmu_exit); +MODULE_ALIAS("platform:arm-smmu-v3-pmcg"); MODULE_DESCRIPTION("PMU driver for ARM SMMUv3 Performance Monitors Extension"); MODULE_AUTHOR("Neil Leeder "); MODULE_AUTHOR("Shameer Kolothum ");